Variation Of Charge Carrier Dynamics For Polycrystalline Perovskite Films By One-Step Solution And Vapor-Deposition Methods

As an emerging semiconductor material,perovskite has achieved huge successes and shown commercial prospects in the photovoltaic industry for more than ten years,and it has striking potential to satisfy special demanding requirements for diverse application purposes.Compared with the rapidly improving efficiency,the research on the underlying physical mechanism of perovskite materials lags behind.For high-performance devices,a high-quality perovskite absorbing layer is essential.High-quality perovskites are directly related to their fabrication methods,but the charge carrier behavior of perovskite films prepared by different methods is still lacking.This thesis compares the carrier behaviors in different fabrication methods and aims at correlating macroscopic photoelectric performance and microscopic carrier dynamics,providing insights for the development of perovskite photovoltaic devices.The main contents include:（1）Simulation and optimization of carrier dynamics models.Based on the one-dimensional perovskite carrier dynamics model along the thickness direction,the particle swarm optimization（PSO）algorithm was introduced,which improved fitting procedures and avoided local optical solutions.Different carrier photonluminescence models were simulated and discussed.The diffusion process was inseparable from the interface recombination,and the surface recombination velocities（SRVs）on both sides were reasonably considered to accurately evaluate the large diffusion coefficient（fast diffusion process）.（2）Comparison of properties of MAPb I₃films prepared by different methods.The high-quality MAPb I₃films with similar grain size and satisfying device performance,prepared by solution-based（one-step spin-coated method）and vapor-deposition method（dual-source co-evaporated method）.Based on previously established description framework of carrier dynamics in perovskite films,the thesis elaborates dynamical parameters of photo-induced charge carriers in one-step spin-coated and dual-source co-evaporation MAPb I₃perovskite films.The vapor-deposited film exhibited single orientation of lattice with less strain showed larger diffusion coefficient,whereas the nucleation growth mechanism of grains was more complex,resulting in more defects in bulky and at the bottom,indicating the large SRVs.For solution fabrication,even though the diffusion coefficient of the film is small,the uniform crystallization process during annealing indeces a tensile strain and leads to the significant SRVs.In summary,this thesis built up analysis of the carrier dynamics according to the actual conditions of the MAPb I₃samples,through reliable simulation and time-resolved spectroscopy methods,and carefully controllable consistence of film samples.The thesis found that variations of strains,lattice orientations,and defect features which are rooted in different fabrication procedures all contribute to the difference in carrier dynamics.